After a vast deal of marching and counter-marching four companies, under Major Dunbar, were left at Boitzenburg, at the junction of the Boitze and the Elbe, while Mackay with the remaining seven was moved to Ruppin. Three days after Mackay's departure, Tilly's army, ten thousand strong, marched up to Boitzenburg and prepared to push forward into Holstein. Dunbar knowing his own weakness had strengthened his defences, but eight hundred men was a small garrison against an army. On the very first night he made a successful sortie; and on the next day the Imperialist army assaulted his works at all points. The first attack was repulsed with loss of over five hundred men to the assailants. Reinforcements were brought up; the attack was renewed and again beaten off, and finally a third and furious onslaught was made on the little band of Scots. In the midst of the fighting the ammunition of the garrison failed and its fire ceased. The Imperialists, guessing the cause, made a general rush for the walls. The Scots met them at first with showers of sand torn from the ramparts, and presently falling in with pike and butt of musket fought the Imperialists hand to hand, and after a desperate struggle drove them out with the loss of another five hundred men. Tilly then drew off and crossed the Elbe higher up, and Dunbar by Christian's order marched proudly out of Boitzenburg. This was the first engagement of Mackay's regiment, a fitting prelude to work that was to come.[145] [Sidenote: October.]